Hi Mike, hi all others,
\begin{CJK*}[dnp]{JIS}{min}
\tableofcontents % <- OK here because it's within \begin{CJK} ... \end{CJK}
\part{1n$bLZ$+$iMn$A$k}
\end{CJK*} Ok. That should work.
But I choose the "dirty" (i. e. ugly) method: I have to edit my toc file by hand, because I want to use bold math symbols in the chapter titles, so I add a CJK-environment as well. So my "solution" was: I wrote \part[some silly stuff -- my prof is an idiot ;-) Die Theorie $\TPA$]{Beweistheorie \`a la\\Gentzen,\\\begin{CJK*}[dnp]{JIS}{min}C]Fb\ (Takeuti) und\\?70f\ (Arai)\end{CJK*}\\[2ex]\thispagestyle{empty} Die Theorie $\TPA$} and edited the produced toc file by hand: Instead of \contentsline {part}{\numberline {II}some silly stuuff -- my prof is an idiot ;-) Die Theorie $\textnormal {\textbf {T}}_{\textnormal {\textbf {PA}}}$}{55} in the toc-file I wrote \contentsline {part}{\numberline {II}Beweistheorie \`a la Gentzen, \begin{CJK*}[dnp]{JIS}{min}C]Fb\ (Takeuti) und ?70f\ (Arai)\end{CJK*}\\Die Theorie $\textnormal {\textbf {T}}_{\textnormal {\textbf {PA}}}$}{55} The output is really beautiful.... Thank you, Mike. Best regards, Ludger